The field of the present invention is recovery of platinum group metals, rhenium and gold from source materials.
Recovery, purification and separation of valuable platinum group metals (platinum [Pt], palladium [Pd], iridium [Ir], rhodium [Rh], osmium [Os], ruthenium [Ru]) and rhenium [Re] and gold [Au] (PGMRA) are typically tedious processes requiring repeated application of pyrometallurgical, hydrometallurgical or electrowinning processes to achieve acceptable metal recovery and metal purity. Chemically simple source materials of platinum group metals, rhenium or gold may lend themselves to relatively straightforward processes with high recovery rates and high metal purity. However, most source materials such as ores, spent catalysts, plating solutions and sludges, ore concentrates and smelter mattes are chemically complex, not only because of the diversity of PGMRA elements but also because of the presence of non-precious metals in the source materials. Recovery, purification and separation of PGMRA elements from these source materials are considered exceedingly difficult.
Current industry practice largely relies on numerous chemical processes. These are at times used in combination with solvent extractions, often with high cost or high toxicity, to recover, separate and purify PGMRA elements. For elements such as Rh, there are no known solvent extraction processes; therefore, exceedingly tedious and very time consuming chemical dissolutions and precipitations are required to recover Rh of sufficient purity. Moreover, separation of Rh from other PGM metals such as Ir and Os is exceedingly difficult by any method.
Recovery of PGMRA elements from acidic solutions with ion exchange resins has had very limited success, in part because highly acidic solutions are required to dissolve the elements and the resins are hot stable in such solutions. For example, Amborane® (Rohm and Haas) recovers PGMRA elements but only from solutions with pH>2. Furthermore, all of the PGMRA elements are so tightly bound to Amborane® they may be separated from the resin as undifferentiated PGMRA only by thermal degradation of the resin. The concentrated PGMRA elements must then be recovered by the same tedious, time consuming and inefficient hydrometallurgical, pyrometallurgical process applied to the source materials, albeit somewhat simplified by exclusion of some of the non-precious metals.
Polyamine composite resins, as disclosed in U.S. Pat. No. 5,997,748 by Rosenberg et al., are specifically designed for recovery and separation of “heavy metals” as defined by Rosenberg et al. “These resins exclude all alkaline and alkaline earth metals and include the transition elements and the elements of the lanthanide and actinide series in the Periodic Table, as well as aluminum tin, lead, titanium and metalloids such as arsenic and selenium” (Column 9, lines 45-50).
Rosenberg et al. disclose non-specifically that the resins find utility in batch processes “for extracting precious metals from aqueous solutions” (column 12, lines 37-39) and “This hydrocarbylated extraction material is suitable for removing heavy metal ions and complex heavy metal ions from contaminated water from ppm range to less than one ppm, and for recovering precious metals” (column 14, lines 27-31). More specifically, Rosenberg et al. contemplate use of specific chelating functional groups of —PR1R2 (R=alkyl or aryl) for Rh+1, Pd+3 and —OCN for low-valent species of Rh+2 and Ru+2 (column 9, Table 1). The disclosure of U.S. Pat. No. 5,997,748 is incorporated herein by reference.